/*
 * [New BSD License]
 * Copyright (c) 2011-2012, Brackit Project Team <info@brackit.org>  
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the Brackit Project Team nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package org.brackit.xquery.util;

import java.util.ArrayList;

import org.brackit.xquery.ErrorCode;
import org.brackit.xquery.QueryException;
import org.brackit.xquery.sequence.ItemSequence;
import org.brackit.xquery.xdm.Expr;
import org.brackit.xquery.xdm.Item;
import org.brackit.xquery.xdm.Iter;
import org.brackit.xquery.xdm.Sequence;

/**
 * 
 * @author Sebastian Baechle
 * 
 */
public abstract class ExprUtil implements Expr {
	private ExprUtil() {
	}

	public final static Item asItem(Sequence res) throws QueryException {
		if ((res == null) || (res instanceof Item)) {
			return (Item) res;
		}
		Iter s = res.iterate();
		try {
			Item item = s.next();
			if (item == null) {
				return null;
			}
			if (s.next() != null) {
				throw new QueryException(ErrorCode.ERR_TYPE_INAPPROPRIATE_TYPE);
			}
			return item;
		} finally {
			s.close();
		}
	}

	public static Sequence materialize(Sequence res) throws QueryException {
		// TODO
		// how to decide cleverly if we should materialize or not???
		if ((res == null) || (res instanceof Item)) {
			return res;
		}
		Iter it = res.iterate();
		try {
			Item first = it.next();
			if (first == null) {
				return null;
			}
			Item second = it.next();
			if (second == null) {
				return first;
			}
			ArrayList<Item> buffer = new ArrayList<Item>();
			buffer.add(first);
			buffer.add(second);
			Item item;
			while ((item = it.next()) != null) {
				buffer.add(item);
			}
			return new ItemSequence(buffer.toArray(new Item[buffer.size()]));
		} finally {
			it.close();
		}
	}
}
